NATURAL SCIENCES OF PHILADELPHIA. 



195 



1888.] 



This spider I described in a verbal coiiimunication to the Academy of 



Natural Sciences of Philadelphia. The speci- 

 mens wei'e found in nests of rolled leaves, 

 after the manner of JEpeira insularis and 

 kindred spiders, and were attached by a taut 

 trapline to the centre of its adjoining snare. 

 Thespecimens then obtained were not mature 

 and on the appearance of Mr. Emerton's de- 

 scriptions of New England Epeiroids I con- 

 cluded that my species was identical with his 

 Epeira silvatica, which it greatly resembles in 

 external form. Subsequently, I received a 

 number of adult specimens from Professor 

 Peckham of Milwaukee, Wisconsin, collected 

 by him in that state, and thereafter, (1886) 



I myself collected a number of the same 

 species in the Adirondack mountains of 



Epeira bicentennaria, female, 

 X "^^ 



New York, in the neighborhood of the Sarauac lakes and elsewhere 

 A study of these led me to conclude that these ex- 

 amples differ from E. silvatica. The species is 15 mm. 

 in length ; is distinguished by two processes on either 

 side of the dorsum of the abdomen at the base. The 

 markings are not unlike those of Epeira silvatica, 

 Fig e i<r.num ^^^^ ^^^^ cpigyuum of the female, differs from that 

 of Epeira silvatica. organ as represented by Emerton.* This is shown 

 by a comparison of Fig. 4, with Fig. 5. This 

 appears to indicate a specific, or at least, a varietal 

 difference between the two animals. According 

 to Emerton in adult females of silvatica "the under 

 side of the abdomen is dark brown without mark- 

 ings;" but the adults of bicentennaria have a 

 yellow lunette on each side of the venter below 

 Fig. 5- Epigynum of the gills, and a yellow circular patch on each side 



E. bicentennaria, lower ~ •in i ^ 



figure side view; upper, of thc mcdiau luie, both at the middle and at trie 



view from the front . i ■ i 



above. spmneret^. The abdomen is somewhat triangular 



in shape. The breadth at the base is a little less than the length ; 

 the color is a yellowish gray with brownish markings. On the 

 basal part is a yellow mark, often assuming the shape of a lyre 



* See Emerton, "New England Spiders of the Family Epeiridae." Trans, 

 Conn. Acad. Vol. vi 1884, PI. xx.xv, fig. 6. 



